The Factory Pattern Is Not What You Think It Is

The factory pattern was not what Doug thought it was a few years ago. Feeling foolish, Doug asked a some co-workers what they knew about the factory pattern. He discovered that he either needs to find some more sophisticated co-workers or the misunderstanding is more common than one might have expected.

In this presentation, Doug will describe and differentiate the factory concept, factory method and abstract factory pattern so that other developers will avoid making the same mistake.

Transcript

1. The Factory Pattern Is Not
   What You Think It Is
   By Doug Corbett
   

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2. What are Patterns?
    Proven software design solutions
    Apply across domains
   

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3. Why You Should Care
    Create more resilient code
   

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4. Why You Should Care
    Create more resilient code
    Benefit from the wisdom of others
   

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5. Gang of Four
    Authored the first book on
   software design patterns.
    23 Patterns
    3 Categories
   Creational Patterns
   Structural Patterns
   Behavioral Patterns
   

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6. Other Influential Books Followed
   

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7. Creational Patterns
   1. Abstract Factory
   2. Builder
   3. Factory Method
   4. Prototype
   5. Singleton
   

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8. Factory Concept (not a pattern)
   

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9. Factory Concept (not a pattern)
   

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10. Factory Concept (not a pattern)
     Pros
     Separates instantiation from representation
     It encapsulates class family instantiation
     Hides public instantiation
     Cons
     Caller has to know what it wants to create
     It violates the Open/Close principle
    

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11. Factory Method Pattern
     Characteristics
     Factories implement an interface
     Specific factory created might not be specified by the
    caller, but by configuration or IoC container
    

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12. Factory Method Pattern
    

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13. Factory Method Pattern
     Pros
     Consumer has no concrete references to factories or
    objects. Loose coupling.
     Initialization can be encapsulated within the factory.
     Can prevent instantiation of objects outside the factory.
     Cons
     Need new factory for each new object
    

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14. Abstract Factory Pattern
     Characteristics
     Similar to Factory Method pattern
     Supports families of objects
    

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15. Abstract Factory Pattern
    

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16. Abstract Factory Pattern
     Pros
     Like Factory Method Pattern, but supports factories
    that can handle families of objects.
     Great for supporting extensibility for other
    departments or third party vendors.
     Cons
     More complex
    

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17. Thank you!
    - Doug Corbett
    

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